Ad hoc testing is an informal and improvisational approach to assessing the viability of a product. An ad hoc test is usually only conducted once unless a defect is found.
Commonly used in software development, ad hoc testing is performed without a plan of action and any actions taken are not typically documented. Testers may not have detailed knowledge of product requirements. Ad hoc testing is also referred to as random testing and monkey testing.
Because the approach is non-methodical, ad hoc testing can miss flaws that would be found in a more structured testing system. However, the lack of formal requirements also means that obvious flaws can be attended to more quickly than if they had to be approached in a more systematic fashion.
Exploratory testing, in which a product is developed, studied and tested simultaneously, is sometimes proposed as a refinement of the ad hoc model.